This is a Conceptual Data Model for Bill of Materials, which is a hierarchical structure. This Model shows that each entry in the Hierarchy can have a 'parent' which is another entry in the Hierarchy. This is indicated as a 'rabbits ear' or associative relationship. Here's a version for a Paper Manufacturing facility with a Warehouse And here is our Toilets Data Model, which uses this BOM Model as a Design Pattern.

Barry Williams
Principal Consultant
Database Answers